/*
 * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package javax.naming;

import java.util.Hashtable;
import javax.naming.spi.NamingManager;
import com.sun.naming.internal.ResourceManager;

/**
 * This class is the starting context for performing naming operations.
 * <p>
 * All naming operations are relative to a context.
 * The initial context implements the Context interface and
 * provides the starting point for resolution of names.
 * <p>
 * <a name=ENVIRONMENT></a>
 * When the initial context is constructed, its environment
 * is initialized with properties defined in the environment parameter
 * passed to the constructor, and in any
 * <a href=Context.html#RESOURCEFILES>application resource files</a>.
 * In addition, a small number of standard JNDI properties may
 * be specified as system properties or as applet parameters
 * (through the use of {@link Context#APPLET}).
 * These special properties are listed in the field detail sections of the
 * <a href=Context.html#field_detail><tt>Context</tt></a> and
 * <a href=ldap/LdapContext.html#field_detail><tt>LdapContext</tt></a>
 * interface documentation.
 * <p>
 * JNDI determines each property's value by merging
 * the values from the following two sources, in order:
 * <ol>
 * <li>
 * The first occurrence of the property from the constructor's
 * environment parameter and (for appropriate properties) the applet
 * parameters and system properties.
 * <li>
 * The application resource files (<tt>jndi.properties</tt>).
 * </ol>
 * For each property found in both of these two sources, or in
 * more than one application resource file, the property's value
 * is determined as follows.  If the property is
 * one of the standard JNDI properties that specify a list of JNDI
 * factories (see <a href=Context.html#LISTPROPS><tt>Context</tt></a>),
 * all of the values are
 * concatenated into a single colon-separated list.  For other
 * properties, only the first value found is used.
 *
 * <p>
 * The initial context implementation is determined at runtime.
 * The default policy uses the environment property
 * "{@link Context#INITIAL_CONTEXT_FACTORY java.naming.factory.initial}",
 * which contains the class name of the initial context factory.
 * An exception to this policy is made when resolving URL strings, as described
 * below.
 * <p>
 * When a URL string (a <tt>String</tt> of the form
 * <em>scheme_id:rest_of_name</em>) is passed as a name parameter to
 * any method, a URL context factory for handling that scheme is
 * located and used to resolve the URL.  If no such factory is found,
 * the initial context specified by
 * <tt>"java.naming.factory.initial"</tt> is used.  Similarly, when a
 * <tt>CompositeName</tt> object whose first component is a URL string is
 * passed as a name parameter to any method, a URL context factory is
 * located and used to resolve the first name component.
 * See {@link NamingManager#getURLContext
 * <tt>NamingManager.getURLContext()</tt>} for a description of how URL
 * context factories are located.
 * <p>
 * This default policy of locating the initial context and URL context
 * factories may be overridden
 * by calling
 * <tt>NamingManager.setInitialContextFactoryBuilder()</tt>.
 * <p>
 * NoInitialContextException is thrown when an initial context cannot
 * be instantiated. This exception can be thrown during any interaction
 * with the InitialContext, not only when the InitialContext is constructed.
 * For example, the implementation of the initial context might lazily
 * retrieve the context only when actual methods are invoked on it.
 * The application should not have any dependency on when the existence
 * of an initial context is determined.
 * <p>
 * When the environment property "java.naming.factory.initial" is
 * non-null, the InitialContext constructor will attempt to create the
 * initial context specified therein. At that time, the initial context factory
 * involved might throw an exception if a problem is encountered. However,
 * it is provider implementation-dependent when it verifies and indicates
 * to the users of the initial context any environment property- or
 * connection- related problems. It can do so lazily--delaying until
 * an operation is performed on the context, or eagerly, at the time
 * the context is constructed.
 * <p>
 * An InitialContext instance is not synchronized against concurrent
 * access by multiple threads. Multiple threads each manipulating a
 * different InitialContext instance need not synchronize.
 * Threads that need to access a single InitialContext instance
 * concurrently should synchronize amongst themselves and provide the
 * necessary locking.
 *
 * @author Rosanna Lee
 * @author Scott Seligman
 * @see Context
 * @see NamingManager#setInitialContextFactoryBuilder NamingManager.setInitialContextFactoryBuilder
 * @since JNDI 1.1 / Java 2 Platform, Standard Edition, v 1.3
 */

public class InitialContext implements Context {

  /**
   * The environment associated with this InitialContext.
   * It is initialized to null and is updated by the constructor
   * that accepts an environment or by the <tt>init()</tt> method.
   *
   * @see #addToEnvironment
   * @see #removeFromEnvironment
   * @see #getEnvironment
   */
  protected Hashtable<Object, Object> myProps = null;

  /**
   * Field holding the result of calling NamingManager.getInitialContext().
   * It is set by getDefaultInitCtx() the first time getDefaultInitCtx()
   * is called. Subsequent invocations of getDefaultInitCtx() return
   * the value of defaultInitCtx.
   *
   * @see #getDefaultInitCtx
   */
  protected Context defaultInitCtx = null;

  /**
   * Field indicating whether the initial context has been obtained
   * by calling NamingManager.getInitialContext().
   * If true, its result is in <code>defaultInitCtx</code>.
   */
  protected boolean gotDefault = false;

  /**
   * Constructs an initial context with the option of not
   * initializing it.  This may be used by a constructor in
   * a subclass when the value of the environment parameter
   * is not yet known at the time the <tt>InitialContext</tt>
   * constructor is called.  The subclass's constructor will
   * call this constructor, compute the value of the environment,
   * and then call <tt>init()</tt> before returning.
   *
   * @param lazy true means do not initialize the initial context; false is equivalent to calling
   * <tt>new InitialContext()</tt>
   * @throws NamingException if a naming exception is encountered
   * @see #init(Hashtable)
   * @since 1.3
   */
  protected InitialContext(boolean lazy) throws NamingException {
    if (!lazy) {
      init(null);
    }
  }

  /**
   * Constructs an initial context.
   * No environment properties are supplied.
   * Equivalent to <tt>new InitialContext(null)</tt>.
   *
   * @throws NamingException if a naming exception is encountered
   * @see #InitialContext(Hashtable)
   */
  public InitialContext() throws NamingException {
    init(null);
  }

  /**
   * Constructs an initial context using the supplied environment.
   * Environment properties are discussed in the class description.
   *
   * <p> This constructor will not modify <tt>environment</tt>
   * or save a reference to it, but may save a clone.
   * Caller should not modify mutable keys and values in
   * <tt>environment</tt> after it has been passed to the constructor.
   *
   * @param environment environment used to create the initial context. Null indicates an empty
   * environment.
   * @throws NamingException if a naming exception is encountered
   */
  public InitialContext(Hashtable<?, ?> environment)
      throws NamingException {
    if (environment != null) {
      environment = (Hashtable) environment.clone();
    }
    init(environment);
  }

  /**
   * Initializes the initial context using the supplied environment.
   * Environment properties are discussed in the class description.
   *
   * <p> This method will modify <tt>environment</tt> and save
   * a reference to it.  The caller may no longer modify it.
   *
   * @param environment environment used to create the initial context. Null indicates an empty
   * environment.
   * @throws NamingException if a naming exception is encountered
   * @see #InitialContext(boolean)
   * @since 1.3
   */
  @SuppressWarnings("unchecked")
  protected void init(Hashtable<?, ?> environment)
      throws NamingException {
    myProps = (Hashtable<Object, Object>)
        ResourceManager.getInitialEnvironment(environment);

    if (myProps.get(Context.INITIAL_CONTEXT_FACTORY) != null) {
      // user has specified initial context factory; try to get it
      getDefaultInitCtx();
    }
  }

  /**
   * A static method to retrieve the named object.
   * This is a shortcut method equivalent to invoking:
   * <p>
   * <code>
   * InitialContext ic = new InitialContext();
   * Object obj = ic.lookup();
   * </code>
   * <p> If <tt>name</tt> is empty, returns a new instance of this context
   * (which represents the same naming context as this context, but its
   * environment may be modified independently and it may be accessed
   * concurrently).
   *
   * @param <T> the type of the returned object
   * @param name the name of the object to look up
   * @return the object bound to <tt>name</tt>
   * @throws NamingException if a naming exception is encountered
   * @see #doLookup(String)
   * @see #lookup(Name)
   * @since 1.6
   */
  @SuppressWarnings("unchecked")
  public static <T> T doLookup(Name name)
      throws NamingException {
    return (T) (new InitialContext()).lookup(name);
  }

  /**
   * A static method to retrieve the named object.
   * See {@link #doLookup(Name)} for details.
   *
   * @param <T> the type of the returned object
   * @param name the name of the object to look up
   * @return the object bound to <tt>name</tt>
   * @throws NamingException if a naming exception is encountered
   * @since 1.6
   */
  @SuppressWarnings("unchecked")
  public static <T> T doLookup(String name)
      throws NamingException {
    return (T) (new InitialContext()).lookup(name);
  }

  private static String getURLScheme(String str) {
    int colon_posn = str.indexOf(':');
    int slash_posn = str.indexOf('/');

    if (colon_posn > 0 && (slash_posn == -1 || colon_posn < slash_posn)) {
      return str.substring(0, colon_posn);
    }
    return null;
  }

  /**
   * Retrieves the initial context by calling
   * <code>NamingManager.getInitialContext()</code>
   * and cache it in defaultInitCtx.
   * Set <code>gotDefault</code> so that we know we've tried this before.
   *
   * @return The non-null cached initial context.
   * @throws NoInitialContextException If cannot find an initial context.
   * @throws NamingException If a naming exception was encountered.
   */
  protected Context getDefaultInitCtx() throws NamingException {
    if (!gotDefault) {
      defaultInitCtx = NamingManager.getInitialContext(myProps);
      gotDefault = true;
    }
    if (defaultInitCtx == null) {
      throw new NoInitialContextException();
    }

    return defaultInitCtx;
  }

  /**
   * Retrieves a context for resolving the string name <code>name</code>.
   * If <code>name</code> name is a URL string, then attempt
   * to find a URL context for it. If none is found, or if
   * <code>name</code> is not a URL string, then return
   * <code>getDefaultInitCtx()</code>.
   * <p>
   * See getURLOrDefaultInitCtx(Name) for description
   * of how a subclass should use this method.
   *
   * @param name The non-null name for which to get the context.
   * @return A URL context for <code>name</code> or the cached initial context. The result cannot be
   * null.
   * @throws NoInitialContextException If cannot find an initial context.
   * @throws NamingException In a naming exception is encountered.
   * @see javax.naming.spi.NamingManager#getURLContext
   */
  protected Context getURLOrDefaultInitCtx(String name)
      throws NamingException {
    if (NamingManager.hasInitialContextFactoryBuilder()) {
      return getDefaultInitCtx();
    }
    String scheme = getURLScheme(name);
    if (scheme != null) {
      Context ctx = NamingManager.getURLContext(scheme, myProps);
      if (ctx != null) {
        return ctx;
      }
    }
    return getDefaultInitCtx();
  }

  /**
   * Retrieves a context for resolving <code>name</code>.
   * If the first component of <code>name</code> name is a URL string,
   * then attempt to find a URL context for it. If none is found, or if
   * the first component of <code>name</code> is not a URL string,
   * then return <code>getDefaultInitCtx()</code>.
   * <p>
   * When creating a subclass of InitialContext, use this method as
   * follows.
   * Define a new method that uses this method to get an initial
   * context of the desired subclass.
   * <blockquote><pre>
   * protected XXXContext getURLOrDefaultInitXXXCtx(Name name)
   * throws NamingException {
   *  Context answer = getURLOrDefaultInitCtx(name);
   *  if (!(answer instanceof XXXContext)) {
   *    if (answer == null) {
   *      throw new NoInitialContextException();
   *    } else {
   *      throw new NotContextException("Not an XXXContext");
   *    }
   *  }
   *  return (XXXContext)answer;
   * }
   * </pre></blockquote>
   * When providing implementations for the new methods in the subclass,
   * use this newly defined method to get the initial context.
   * <blockquote><pre>
   * public Object XXXMethod1(Name name, ...) {
   *  throws NamingException {
   *    return getURLOrDefaultInitXXXCtx(name).XXXMethod1(name, ...);
   * }
   * </pre></blockquote>
   *
   * @param name The non-null name for which to get the context.
   * @return A URL context for <code>name</code> or the cached initial context. The result cannot be
   * null.
   * @throws NoInitialContextException If cannot find an initial context.
   * @throws NamingException In a naming exception is encountered.
   * @see javax.naming.spi.NamingManager#getURLContext
   */
  protected Context getURLOrDefaultInitCtx(Name name)
      throws NamingException {
    if (NamingManager.hasInitialContextFactoryBuilder()) {
      return getDefaultInitCtx();
    }
    if (name.size() > 0) {
      String first = name.get(0);
      String scheme = getURLScheme(first);
      if (scheme != null) {
        Context ctx = NamingManager.getURLContext(scheme, myProps);
        if (ctx != null) {
          return ctx;
        }
      }
    }
    return getDefaultInitCtx();
  }

// Context methods
// Most Javadoc is deferred to the Context interface.

  public Object lookup(String name) throws NamingException {
    return getURLOrDefaultInitCtx(name).lookup(name);
  }

  public Object lookup(Name name) throws NamingException {
    return getURLOrDefaultInitCtx(name).lookup(name);
  }

  public void bind(String name, Object obj) throws NamingException {
    getURLOrDefaultInitCtx(name).bind(name, obj);
  }

  public void bind(Name name, Object obj) throws NamingException {
    getURLOrDefaultInitCtx(name).bind(name, obj);
  }

  public void rebind(String name, Object obj) throws NamingException {
    getURLOrDefaultInitCtx(name).rebind(name, obj);
  }

  public void rebind(Name name, Object obj) throws NamingException {
    getURLOrDefaultInitCtx(name).rebind(name, obj);
  }

  public void unbind(String name) throws NamingException {
    getURLOrDefaultInitCtx(name).unbind(name);
  }

  public void unbind(Name name) throws NamingException {
    getURLOrDefaultInitCtx(name).unbind(name);
  }

  public void rename(String oldName, String newName) throws NamingException {
    getURLOrDefaultInitCtx(oldName).rename(oldName, newName);
  }

  public void rename(Name oldName, Name newName)
      throws NamingException {
    getURLOrDefaultInitCtx(oldName).rename(oldName, newName);
  }

  public NamingEnumeration<NameClassPair> list(String name)
      throws NamingException {
    return (getURLOrDefaultInitCtx(name).list(name));
  }

  public NamingEnumeration<NameClassPair> list(Name name)
      throws NamingException {
    return (getURLOrDefaultInitCtx(name).list(name));
  }

  public NamingEnumeration<Binding> listBindings(String name)
      throws NamingException {
    return getURLOrDefaultInitCtx(name).listBindings(name);
  }

  public NamingEnumeration<Binding> listBindings(Name name)
      throws NamingException {
    return getURLOrDefaultInitCtx(name).listBindings(name);
  }

  public void destroySubcontext(String name) throws NamingException {
    getURLOrDefaultInitCtx(name).destroySubcontext(name);
  }

  public void destroySubcontext(Name name) throws NamingException {
    getURLOrDefaultInitCtx(name).destroySubcontext(name);
  }

  public Context createSubcontext(String name) throws NamingException {
    return getURLOrDefaultInitCtx(name).createSubcontext(name);
  }

  public Context createSubcontext(Name name) throws NamingException {
    return getURLOrDefaultInitCtx(name).createSubcontext(name);
  }

  public Object lookupLink(String name) throws NamingException {
    return getURLOrDefaultInitCtx(name).lookupLink(name);
  }

  public Object lookupLink(Name name) throws NamingException {
    return getURLOrDefaultInitCtx(name).lookupLink(name);
  }

  public NameParser getNameParser(String name) throws NamingException {
    return getURLOrDefaultInitCtx(name).getNameParser(name);
  }

  public NameParser getNameParser(Name name) throws NamingException {
    return getURLOrDefaultInitCtx(name).getNameParser(name);
  }

  /**
   * Composes the name of this context with a name relative to
   * this context.
   * Since an initial context may never be named relative
   * to any context other than itself, the value of the
   * <tt>prefix</tt> parameter must be an empty name (<tt>""</tt>).
   */
  public String composeName(String name, String prefix)
      throws NamingException {
    return name;
  }

  /**
   * Composes the name of this context with a name relative to
   * this context.
   * Since an initial context may never be named relative
   * to any context other than itself, the value of the
   * <tt>prefix</tt> parameter must be an empty name.
   */
  public Name composeName(Name name, Name prefix)
      throws NamingException {
    return (Name) name.clone();
  }

  public Object addToEnvironment(String propName, Object propVal)
      throws NamingException {
    myProps.put(propName, propVal);
    return getDefaultInitCtx().addToEnvironment(propName, propVal);
  }

  public Object removeFromEnvironment(String propName)
      throws NamingException {
    myProps.remove(propName);
    return getDefaultInitCtx().removeFromEnvironment(propName);
  }

  public Hashtable<?, ?> getEnvironment() throws NamingException {
    return getDefaultInitCtx().getEnvironment();
  }

  public void close() throws NamingException {
    myProps = null;
    if (defaultInitCtx != null) {
      defaultInitCtx.close();
      defaultInitCtx = null;
    }
    gotDefault = false;
  }

  public String getNameInNamespace() throws NamingException {
    return getDefaultInitCtx().getNameInNamespace();
  }
};
